Characteristics of Successful Single Pivotal Trials

Single pivotal trials are now a very important part of the regulatory evidence landscape, particularly when a strong study is supported by wider clinical data

Insights into non-oncology, non-orphan approvals shows why trial design, statistical strength, disease severity, and supporting evidence all matter when one pivotal study carries much of the efficacy case.

Image

Why Are Single Pivotal Trials Important Now?

For decades, regulatory practice commonly relied on more than one adequate and well-controlled clinical trial to establish efficacy.

Yet regulators have long recognised that a single well-designed study can sometimes provide sufficient evidence when the overall evidence package is persuasive.

The issue is not simply whether one trial is enough but whether that trial provides a credible, clinically relevant, and sufficiently precise estimate of treatment effect.

Between 2012 and 2016, across the European Union and/or the United States, 23 novel drugs received approval for 27 indications supported by a single pivotal clinical trial.

For these approvals, the study population really mattered.

These were not oncology or orphan-drug approvals, where smaller populations or serious disease can make conventional evidence generation more difficult.

The findings therefore show that single pivotal trials were also used in broader therapeutic areas when the surrounding evidence supported the regulatory case.

Twenty-three of the 27 pivotal trials (85%) were randomised and controlled, while 13 were placebo-controlled and 10 used an active comparator. Four trials were open-label and uncontrolled and every pivotal trial was multicentre.

Sponsors should take note of that analysis. A single pivotal trial does not necessarily mean a minimal trial. In many instances, the central study is usually comparative, multicentre, and designed to produce a direct test of efficacy.

View interview How AI Is Opening New Opportunities in Fertility Care for Pharma

How AI Is Opening New Opportunities in Fertility Care for Pharma

"If I had to get great minds in a room, I'd be looking at it from a tech perspective. How can we take all this knowledge, apply it to policies that can be easily distributed?” Clara Toombs, Fertilia AI.

Image

What Do the Numbers on Single Pivotal Trials Reveal About Trial Strength?

The scale of single pivotal trials usually vary substantially in terms of the median number of patients enrolled, ranging from only handfuls to tens-of-thousands or even more.

This wide range shows that there is no universal sample size that defines a credible single-trial evidence package.

Endpoint selection also usually varies.

Out of the successful 27 studies from 2012 through 2017, clinical outcomes were used as the primary endpoint in 12 of the 27 trials (44%). Five trials (19%) used clinical scales, while 10 (37%) relied on surrogate markers. The surrogate endpoints had regulatory support in the context of the approved indications.

In the 27 studies, the statistical results were particularly notable. Among the 16 superiority trials, every primary endpoint met its prespecified statistical criterion with a P-values of 0.005 or less. Non-inferiority trials met their prespecified margins based on confidence intervals.

This does not mean that statistical significance alone establishes clinical value.

A small P-value can indicate that an observed difference is unlikely to be explained by random variation under the statistical model, but it does not by itself establish the size, durability, or practical importance of a treatment benefit.

The dataset of the 27 successful single pivotal trials provides useful examples of how different evidence structures can support a single pivotal trial.

Cangrelor, for example, was evaluated against clopidogrel in more than 11,000 patients, with the primary outcome occurring in 4.7% of patients receiving cangrelor compared with 5.9% receiving the comparator, producing an odds ratio of 0.78 and P = 0.005.

By contrast, some trials relied on non-inferiority designs, where the critical question was whether the treatment remained within a predefined margin rather than whether it produced statistically superior outcomes.

The uncontrolled trials also illustrate why context matters so much.

Daclatasvir was supported by virologic response rates of at least 89%, while susoctocog alfa produced a 100% response rate for serious bleeding episodes. Lomitapide produced a 40% reduction from baseline in low-density lipoprotein cholesterol.

These results were considered within their specific regulatory and clinical settings rather than treated as interchangeable evidence.

Image

The Evidence Around Single Pivotal Trials Is Vital

One of the clearest points of information for single pivotal trials is that the study itself is rarely the only efficacy information available to regulators.

In almost every indication, one or more additional nonpivotal clinical trials can be classified as supportive in the regulatory review documents.

These studies can also vary widely. Some may not be designed or powered primarily to demonstrate efficacy. Instead, they may focus on pharmacokinetics, safety, tolerability, dose selection, or other development questions while still contributing useful efficacy information.

This creates an important distinction for clinical development teams. A single pivotal trial can be the principal efficacy study without being the only source of evidence.

The broader programme can provide independent signals that help regulators interpret the pivotal result.

Supportive evidence is also usually not presented consistently in product labelling. That matters because the evidence package considered during regulatory review can be broader than the headline pivotal trial reported in public-facing materials.

The role of disease severity is another important characteristic to consider when designing single pivotal trials.

In the analysis of the 27 trials, many indications involved conditions such as cardiovascular events, HIV infection, serious bacterial infections, and chronic hepatitis C. Seven of the 13 novel drugs included in the U.S. analysis had also received Food and Drug Administration (FDA) Fast Track or Breakthrough Therapy Designation.

Therefore there is a broader regulatory principle at play, which is that the acceptability of a single pivotal trial is influenced by the clinical context and the availability of corroborating evidence. It is not simply a statistical shortcut.

Read Maximise Pharma Innovation With Quality-by-Design

Maximise Pharma Innovation With Quality-by-Design

Find out how Quality-by-Design improves reliability and compliance in pharma and how you can maximise innovation through quality-based pharma development systems.

Image

How to Design Studies With Sufficient Single-Trial Evidence

For clinical development teams, the central lesson for single pivotal trials is to think about the evidence package as a connected system.

If one pivotal trial is expected to carry most of the efficacy burden, its design needs to withstand scrutiny across population, comparator, endpoint, analysis, and generalisability.

A sponsor considering this route should pay particular attention to:

• Comparative strength: Randomisation and an appropriate control can provide a stronger basis for causal inference than an uncontrolled design.
• Endpoint credibility: Clinical outcomes may offer direct evidence of benefit, while surrogate endpoints require an appropriate regulatory and scientific rationale.
• Statistical precision: The trial should provide sufficiently precise estimates of effect, not merely a nominally positive result.
• External support: Nonpivotal studies can contribute independent evidence across different populations, designs, or development stages.
• Regulatory alignment: Sponsors should engage regulators early when the development strategy depends heavily on a single pivotal study.

This thinking remains relevant as Clinical Development becomes more flexible.

The FDA’s 2023 draft guidance describes how one adequate and well-controlled clinical investigation can be combined with confirmatory evidence to establish substantial evidence of effectiveness.

The agency further states that confirmatory evidence can come from different sources, including clinical, mechanistic, or animal data, depending on the circumstances.

The European Medicines Agency (EMA) also retains specific guidance on the use of one pivotal study in Phase III development and has continued to refine its thinking around single-arm pivotal evidence.

The 2024 EU reflection paper makes clear that randomised controlled evidence remains the regulatory standard where feasible, while single-arm approaches require justification.

The regulatory landscape therefore points towards a more nuanced question than “one trial or two?” The more useful question is whether the complete evidence package answers the key efficacy and safety questions with enough reliability for the proposed indication.

Image

What Does Single-Trial Evidence Mean for Clinical Development Teams?

Single pivotal trials should not replace multiple confirmatory studies in all instances. On the contrary, approvals based on one pivotal trial in non-oncology, non-orphan settings are often built around large, multicentre, controlled studies with strong primary results and additional clinical evidence.

This shifts the strategic focus from trial count to evidence architecture. A single pivotal trial can reduce duplication and concentrate resources, but it also places greater importance on the quality and breadth of everything surrounding that trial.

Current regulatory thinking reinforces that point. The FDA and EMA guidelines, respectively, both recognise circumstances in which one pivotal study can form part of a sufficient evidence package, while emphasising the need for appropriate supporting evidence and scientific justification.

The most important planning question is whether the development programme has enough independent evidence to make the pivotal result credible, interpretable, and relevant to the patients who will ultimately receive the medicine.

At Pharmatica, we track the decisions shaping the Clinical Compass, from pivotal trial design and statistical strategy to regulatory evidence and development efficiency. Our Insights connect clinical data with the choices that determine how medicines progress towards patients.

Pharmatica: Insight. Connection. Impact.